Electrolytic production of metallic uranium



Aug. 22, 1950 R. ROSEN 2519,792

ELECTROLYTIC PRODUCTION oF METALLIC URANIUM Filed April 10. 1942 @bhw/@.3 I

Patented Aug. 22, 1950 ELECTROLYTIC PRODUCTION OF METALLIC URANIUM Raphael Rosen, Elizabeth, N. J., assignor, by mesne assignments, to the United States of America as represented by the United States Atomic Energy Commission Application April 10, 1942, Serial No. 438,356

4 Claims, (Cl. 204-64) The present invention relates to the preparation of heavy metals, such as uranium, tungsten and the like by electrolysis and more specifically to the electrolysis of single fluorides of such metals. The invention will be fully understood from the following descriptionV of the drawing.

The drawing is a semi-diagrammatic view in sectional elevation of an electric cell for producing metals and especially uranium.

Referring to the drawing, I denotes a vessel made of carbon in which the electrolyte is indicated generally at 2. The carbon vessel is preferably the anode of the cell and the positive pole is shown at 3 connected to the positive wire of any convenient source of direct electric current, which source, however, is not shown.

The carbon anode is adapted to be maintained at a high temperature and is for this reason surrounded by insulation 4 in which is embedded electrical heating elements 5. The whole is then surrounded by.a steel shell 6. A pipe 'I is provided connecting the interior of the carbon vessel with the outside atmosphere so that gas rproduced in the electrolysis may be drawn oli, as will be disclosed. This gas may be Concentrated and collected during the process, although particular apparatus for this purpose is not shown.

The top of the cell container I is covered by a cover plate 8 with a central hole 9, through which the cathode ID projects into the cell inf terior and well below the surface of the electrolyte. The cover plate is insulated from the cathode by an annular member II which surrounds the hole 9 and is provided with an apron which extends down into the hole. This annular member II is made of compressed asbestos or other insulating material and, as will readily be understood, prevents all contact between the cathode I and the cover plate 8, especially when the cathode is being withdrawn, for example, by the eye bolt I2. A circular shield I 3 is rigidly attached to the metal cathode and extends outwardly at right angles to the axis of the cathode so that when the latter is in the cell as shown, this shield lits tightly over the insulating member II and completely closes the hole 9 from the atmosphere and thus prevents the escape of gas therefrom. The negative pole of the electrical source is connected at I4.

While the cell described above is quite satisfactory, it may be constructed otherwise and of other materials; for example, the carbon anode may be replaced by other materials such as a container made of beryllium or silicon, but it must be appreciated that these materials will find their Way into the electrolyte and thus into the product in small quantities and consequently depending upon the particular use to which the product is to be applied, a judicious selection of the material of the cathode should be made. Similarly, the anode is preferably of metallic molybdenum, but it may be of tungsten or uranium or even of carbon or other non-reactive materials, which materials, however, are good conductors of electricity. Similarly, the cell is shown as being heated electrically but this, while convenient, is not necessary as it may be heated in a bath of lead or fused solids or may be directly fired with gas or oil. One convenient method for heating the cell is to provide circulating legs; that is to say, tubes from the bottom of the cell bath to an upper portion thereof. These tubes are then heated and the electrolyte flows by thermal circulation from the cell through the tubes and back to the cell again. In this manner the temperature can readily be maintained at the desired point.

In the operation of my process which is conducted in batch the electrolyte, consisting of a mixture of alkali or alkaline earth halides, is placed in the cell container and heated to the fusing point. The preferred electrolyte is a mixture of calcium and sodium chlorides. Ordinarily the eutectic mixture, containing about 51.5 mol percent of calcium chloride is employed and this has a fusing point of about 505P C. Any temperature above this may be used so long as it is not high enough to cause volatilization. However, since the bath composition may change from time to time, it is preferred to use a temperature of about 800 C.; that is to say, just above the fusing points of pure calcium chloride and also above that of sodium chloride.

To this bath uranium tetrauoride, UFi, is added from time to time and is decomposed by the action of the electric current. About six volts is required for the cell. rIhe period over which the cell operates may vary considerably but may be conveniently about 30 minutes, during which time al1 of the uranium or other heavy metal is plated out of the electrolyte in the form of a dark powder which adheres to the metal cathode.

After the metal has been desposted, the current is shut off and the cathode is withdrawn from the cell and the deposited metal may be readily scraped ofi by any convenient means and is washed with an acid solution and then with water to remove all traces of the electrolyte.

As stated above, the bath consists preferably of the eutectic mixture of calcium and sodium chlorides and it may be reused time after time. It will, however, gradually be converted to fluorides due to the action of the elemental uorine Which is released at the anode during the electrolysis. Thus, the uorine which is released will be contaminated'witna small amount ofchlorine if chlorides employed in the bath. If Vit is de= sired to recover a high purity fluorine gas, it is preferred to employ lluorides as the bath con-.-v

and 850 C. The electrolyte consists of the-elrtectic mixture of 51.5 mol per cent calcium chloancisediumvchloride and. to this bathv added @ik norufrdsof uranium tetrailuoride; that is;

tu say;ratiio oli' lpouncl thereof, to; 3 pounds of;

the; electrolyte bath. The current. is thenturned on, using six volts andaloout: 4.0.0(1' a-mpcres 'for afperiod ol?" about, 3o;` minutes. At. the end of' this' timethe uranium is completely deposited.' The currentlis therrshut. off and the cathode' With.- draW-n from the cell.. Approximately li pounds of uranium. is recovered from the: cathode as a darle pow-der. An additional quantity oi uranium t@traJihioridie is: then added to the bath, the.v cath.- ode replaced. and the eurent again turned on so thatthe cycle is repeated- `Afterr a considerableperiod oftime the melt ing-'point ofl the bath gradually increases due to the substitution of! the fluoride for the chloride and-it maybe discardedl and replaced. Thepresent invention is not to be considered as limited by any'thecry of operation nor to the particular-metalproduced or materials of construction set forth, but only by the following claims.

I claim-tv 1'.' 'rrthe process for' produc-ing metallic-'uranium by electrolyzingf a uranium salt in a. fused bath consisting essentially of mixed alkali and alkaline earth halides, the improvement in which anhydrous uranium tetra fluoride is the uranium salt, said fluoride being introduced into the-fused bathl in the ratio of 1 part uranium tetra fluoride toV 3 parts of saidbath, and maintaining a tem- 4 perature of between about 800 C. and 850 C. during the electrolysis.

2. In the process for producing metallic uranium by electrolyzing a uranium -salt in a, fused bath consisting essentially of a mixture of sodium and calcium halides, the improvement in which anhydrous uranium tetrefrluoride is the uranium salt, said fluoride being introduced into the fused bath in the ratio of 1 part uranium tetra fluoride to 3 parts of said lbath, and maintaining a tempeinture off between about 800 C. and 850 C. during the electrolysis.

Ei; In. the.y process for producing metallic uranium.- by electrolyzing a uranium salt in a fuzed bath consisting essentially of a, mixture of sodium and calcium uorid'es, the improvement in which anhydrousuranium tetra fluoride is the uranium salt, said fluoride being introduced into the fused loatlrinA the ratio of 1 part uranium tetra iluoride to 3 parts of said bath, and maintaining a temperature -cfbetween about 800"` C.v and 8509- C. during the, electrolysis..V Y

4.111. the. process for producing metallic uranilnn by electrolyzins a-uranium salt inca fused. bathconsistine essentially-of a mixture ci sodium and calcium chlorides, the. improvement in which anhydrous.uraniumtetra uoride is the uranium salt,V saidfluoride being introduced into the fused bath in the ratioof. lpart uranium, tetra' fluoride to, 3 parts of said bath. and maintaining a temperature ofhetween about 800@ C. and 850 C. during the electrolysis.

RAPHAEL RQSEN.

REFERENCES, Gl'lED The following. reierencesare of` record; in th lcof thjspatent; Y Y

UNITED VSflrYISES PATENTS Number Name Date.. 1,815,054 Driggs July 21 1931' 1,821,176 Drggsxet Sept. 1, 1931 1,835,025 Briggs et. al. ..'De0'. 8, 1931 13,842,254 Drgggse Jan. 19,1932 1,861.i625 Drggseta June 7;, 1932l 

1. IN THE PROCESS OF PRODUCING METALLIC URANIUM BY ELECTROLYZING A URANIUM SALT IN A FUSED BATH CONSISTING ESSENTIALLY OF MIXED ALKALI AND ALKALINE EARTH HALIDES, THE IMPROVEMENT IN WHICH ANHYDROUS URANIUIM TETRA FLUORIDE IS THE URANIUM SALT, SAID FLUORIDE BEING INTRODUCED INTO THE FUSED BATH IN THE RATIO OF 1 PART URANIUM TETRA FLUORIDE TO 3 PARTS OF SAID BATH, AND MAINTAINING A TEMPERATURE OF BETWEEN ABOUT 800*C. AND 850*C. DURING TH ELECTROLYSIS. 